The present invention relates to a rotary support for use in a machine tool. More particularly, the present invention relates to a rotary support to be used for transporting workpieces into the region of operation of a tool.
There are already known various machine tools, for instance such in which a plurality of tools or of workpieces is mounted on a rotary support which revolves about its axis so as to bring the tools or the workpieces into a plurality of positions, whereupon the rotary support is arrested so that the particular cutting or other material-removing operation can be performed on the workpiece. This movement and arresting will be hereinafter referred to as indexing. When the rotary support is used for supporting the workpieces, it includes a plurality of workpiece carriers to which the workpieces can be secured, and some of the carriers in any indexed position of the rotary support may be driven into rotation, while at least one of the carriers may be stopped in order to be able to remove a workpiece which has previously been acted upon by the tool, and to replace the same by a new workpiece. This arrangement is very useful and has found widespread application in connection with machine tools, such as lathes. The advantage of this arrangement is to be seen in the fact that the replacement of a finished workpiece may be conducted simultaneously with performing the material-removing operation on a different workpiece, which cuts down on the time needed for finishing the article by significantly reducing the idle time of the machine.
In conventional machine tools utilizing a revolving support of the above-discussed type, the supporting surfaces of the carriers which determine the position of the workpieces with respect to the rotary support and thus with respect to the material-removing tool, are usually located in the same plane. It is already known to so arrange the rotary support that the plane in which the supporting surfaces are located extends substantially horizontally, substantially vertically, or at an angle to the horizontal. In all of these conventional arrangements, however, the supporting surfaces are located in the same plane or at least in parallel planes, regardless of the position which each particular carrier assumes.
Experience with these arrangements has shown that some disadvantages attach thereto, regardless of the angle which the above-mentioned plane encloses with the horizontal. So, for instance, when the supporting surfaces are located in a substantially vertical plane, it is necessary during the removal of the finished workpiece and its replacement by a new one not only to overcome the weight of the workpiece, but also to compensate for the moment which attempts to tilt the workpiece away from the supporting surface. This task must be performed by the conveyor or a similar manipulating arrangement which removes and delivers the workpieces prior to the attachment of the respective workpiece to the workpiece carrier, or the carrier itself or the arrangement for attaching the workpiece to the carrier must perform these two tasks. When workpieces of relatively large dimensions and thus of considerable weight are to be thus transported and attached to the respective carriers, and when these operations are to be performed manually, a high degree of skill is required from the operator, and also a considerable expenditure of energy. On the other hand, when the transportation and attaching to the carriers is performed by an automatically working mechanism, the latter will have to be rather complex, particularly when the cylindrical workpieces which are to be shaped in the machine tool by material-removing operations are elongated since then it is customary to transport these workpieces in substantially upright position, so that these workpieces must be tilted into a substantially horizontal position prior to their clamping in or other attachment to the carrier. In order to avoid the need for tilting the elongated cylindrical workpieces prior to their attachment to their respective carriers, it has already been proposed to so arrange the rotary support that the supporting surfaces of the respective carriers are located in a substantially horizontal plane. Other advantages of this horizontal arrangement of the support surfaces are that the carriers themselves will support the workpieces, thus overcoming their weights, and that the tendency of the workpieces to tilt away from the supporting surfaces is not present in this case. Thus, the handling of the workpieces is considerably simplified in this arrangement when compared to the rotary supports in which the supporting surfaces are located in the vertical plane; however, the turnings or chips which are removed from the workpiece during the material-removing operation will fall onto and accumulate on the rotary support and on the carriers where they will interfere with the proper operation of the carriers, unless they are periodically and rather often removed. However, experience has shown that the removal of the turnings or chips is rather difficult and cannot always be performed to complete satisfaction.
Finally, when the supporting surfaces of the carriers are located in a plane which extends at an angle to the horizontal, not only is it not assured that the turnings or chips are removed from the rotary support and from the carriers at each material-removing operation, but also the workpiece transporting and attaching operations are rather complicated.
In order to avoid the above-mentioned disadvantages, it has already been proposed to mount a workpiece carrier on a support which is mounted on the frame of the machine tool for pivoting about a substantially horizontal axis between one position in which the support surface extends substantially horizontally, and another position in which the support surface extends substantially vertically, the material-removing operation being performed when the support surface is in the latter position. However, even this arrangement is disadvantageous, in that this arrangement is capable of handling only a single workpiece at a time, that is the workpiece must be first attached to the carrier, then the support is pivoted, then the material-removing operation performed, and the support is subsequently pivoted back into its initial position, and only then the workpiece which has been just operated on is removed and replaced by a new workpiece. This, of course, involves a substantial increase in the idle time of the machine tool, since the time period for pivoting the support between the two positions thereof is to be added to the time needed for positioning the workpiece on the carrier and removing the same therefrom subsequently to the performance of the material-removing operation.